I've owned both because I like the flexibilty which modelling brings to the party. I used a Line 6 Bass Pod XT Live for a while and it was fine...until it developed a fault where the patches would turn themselves on or off at random.
In looking for a replacement I realised that I had been disenchanted with Line 6 for a while, because they had simply lost interest in producing products for bass and had left those of us who had spent good money on their products in a blind alley. I could have bought another Line 6 product, but even then - easily 2 years ago - the only option would have been to buy a device aimed at guitarists, spend extra for a 'bass pack' and essentially pay for a whole load of amp models and FX that I would never use.
So I bought a Zoom, which sounds a lot better and is easier to program.